[gnome-db]Updates to the MySQL provider

[Vivien Malerba <malerba TorresQuevedo HispaLinux es>]

Hi all!

I've commited my changes to the MySQL provider. So far I have modified
the schemas functions for the tables (mainly to include comments), the
columns (to include default values, right data type, etc) and the data
types one (from scratch). These schemas are almost up to date with the
Postgres provider in what information they return.

I will continue with the functions and aggregates...

If you have any comments or find bugs, please
tell me.

Cheers,

Vivien